The Alaska Peninsula is a peninsula extending about 800 km (497 mi) to the southwest from the mainland of Alaska and ending in the Aleutian Islands. The peninsula separates the Pacific Ocean from Bristol Bay, an arm of the Bering Sea.
In literature (especially Russian) the term ‘Alaska Peninsula’ was used to denote the entire northwestern protrusion of the North American continent, or all of what is now the state of Alaska, exclusive of its panhandle and islands. The Lake and Peninsula borough, the Alaskan equivalent of a county, is named after the peninsula.
The Aleutian Range is a highly active volcanic mountain range which runs along the entire length of the Peninsula. Within it lie Wildlife Refuges, including the Katmai National Park and Preserve, the Aniakchak National Monument and Preserve and the Becharof National Wildlife Refuge, the Alaska Peninsula National Wildlife Refuge, and the Izembek National Wildlife Refuge.
The southern side of the Alaska Peninsula is rugged and mountainous, created by the uplifting tectonic activity of the North Pacific Plate subsiding under a western section of the North American Plate; the northern side is generally flat and marshy, a result of millennia of erosion and general seismic stability. The northern and southern shores are likewise quite different. The northern Bristol Bay coastal side is generally turbid and muddy, experiences tidal extremes, and is relatively shallow; the Pacific side has relatively small tidal activity and is deep and clear.